EP0031661A1

EP0031661A1 - Yarn feeding apparatus

Info

Publication number: EP0031661A1
Application number: EP80304469A
Authority: EP
Inventors: Katsume Hasegawa; Takahiro Kawabata; Hiroshi Ueda
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 1979-12-12
Filing date: 1980-12-11
Publication date: 1981-07-08
Also published as: JPS5682761A; US4362260A; EP0031661B1; DE3067212D1

Abstract

A yarn feeding apparatus for transferring continuously fed yarn from a yarn supply source to a yarn taking-up apparatus comprises rotating roller (1) having a large diameter portion (1a) over which the travelling yarn passes along a yarn path Y₂ during normal feeding of the yarn, a small diameter portion (1 b) over which the yarn passes along yarn path Y_o during the yarn threading operation, yarn hooking means (1c) at the edge of the peripheral surface of the large diameter portion and means (6,13) for shifting the path of the travelling yarn from Y_o towards the larger diameter portion (1 b), so that the yarn is caught by yarn hooking means (1c) and moves to yarn path Y₂.

Two such stepped rollers may be provided in series, or there may be one plain roller and one stepped roller travelling at different speeds, so that the yarn is drawn.

Description

This invention relates to a yarn feeding apparatus for transferring a synthetic yarn supplied continuously from a yarn supply source to a yarn taking-up apparatus at a high feeding speed.
Generally, a synthetic yarn is produced by extruding a polymer such as polyamide or polyester in a molten state from a spinning apparatus to form continuous filaments, cooling the filaments and taking-up the filaments by a yarn taking-up apparatus after the filaments have passed through a feeding apparatus for the filaments. The feeding apparatus usually comprises at least one positively rotating roller (usually called a godet roller) over which the filaments are led and by which the filaments are advanced.
For threading the yarn from the spinning apparatus to the taking-up apparatus through the feeding apparatus, an air ejector (usually called a suction nozzle or gun in a factory) is generally employed. The travelling yarn supplied continuously from the spinning apparatus is sucked and drawn off by the suction nozzle. The yarn is threaded between the spinning apparatus and the taking-up apparatus by moving the suction nozzle by a person along a thread line formed mainly with one or more positively rotating rollers and several yarn guides positioned in appropriate places.
A winder comprising a rotatable tube or bobbin on which the yarn is wound up is usually employed as the taking-up apparatus.
In recent years, the winding speed of yarn has been increased and is often a speed of about 6,000 metres per minute (m/min.) or more, as disclosed for example in U.S. Patent No.4 134 882.
If the suction force of the suction nozzle is not sufficient, the yarn cannot be drawn off by the suction force of the suction nozzle from the positively rotating roller after threading the yarn on the roller on account of the adhesion of the yarn to the surface of the roller or the air stream generated around the roller by its rotation, as a result of which the yarn rolls in on the roller and the expected operation of threading of the yarn to the winder through the positively rotating roller cannot be effected. The difficulty in the threading operation becomes greater as the yarn transfer speed on the positively rotating roller becomes higher and the volume of the yarn becomes greater, that is, as a greater force becomes necessary for drawing off the yarn from the roller.
Even with an excellent commercially ava.ilable suction nozzle, used at the largest volume of air under pressure, the suction force of the nozzle is only capable of drawing off a yarn having a travelling speed of from about 3,500 to about 4,000 m/min at the most.
On the other hand, several suction nozzles having high performance have been proposed, one of which is disclosed in Japanese Patent Publication No.49778/72. For employing such a high performance; suction nozzle for threading, it is necessary to have a'pressure chamber of a large capacity and compressed air at high pressure in order to maintain the high suction force. Further, such a high performance suction nozzle has the following problems:

(A) worsening of work environment due to extremely loud noise generated upon release of the compressed air.
(B) large consumption of the compressed air results in the continuous yarn threading operation not being economical.
Subsequent work must wait until the pressure recovers. During the wait, waste yarns are generated in great quantities.
(C) even a slight drop in the suction force leads to a failure in the yarn threading operation.

In a method of winding of a high speed spun yarn, Japanese Laid-Open Patent No.8111/77 discloses a method which uses a stepped roller as a yarn feeding apparatus and in which the yarn is passed over a small diameter portion of the stepped roller at the time of the yarn threading operation so that the tension of the travelling yarn between the positively rotating roller and the winder is maintained higher than the tension at the time of normal winding. After threading the yarn to the winder, the travelling yarn is moved to a large diameter portion of the roller by a yarn shifting guide. This method was developed with the object of increasing the success ratio of threading to a winder; therefore it discloses a stepped roller having a diameter ratio of a few percent between the large diameter portion and the small diameter portion. If the diameter ratio is increased on the stepped roller, the travelling yarn cannot be moved from the small diameter portion to the large diameter portion by the yarn shifting guide because of a large difference in height between the surface of both the portions.
It is an object ot the invention to provide a yarn feeding apparatus for transferring a synthetic yarn at high speed in normal feeding operation, arranged between a yarn supply source and a yarn taking-up apparatus, in which the disadvantages described are overcome and by which a threading of the yarn from the yarn supply source to the yarn taking-up apparatus through the yarn feeding apparatus can be carried out employing a conventional commercially available nozzle.
Another object is to provide a yarn feeding apparatus for transferring or transferring and drawing, a synthetic freshly spun yarn supplied continuously from a spinning apparatus to a yarn winder at high speed in normal feeding operation, which is capable of threading the yarn from the spinning apparatus to the winder through the feeding apparatus with a conventional commercially available suction nozzle.
According to the invention, the yarn feeding apparatus comprises a stepped roller, positively rotated by driving means, which has a large diameter portion over which the travelling yarn passes during the normal feeding of the yarn and a small diameter portion over which the travelling yarn passes during the threading operation, and further the stepped roller has yarn hooking means at the edge of the peripheral surface of the large diameter portion on the side adjacent the small diameter portion.
Means are provided at the upstream side of the stepped roller for shifting the path of the travelling yarn from the small diameter portion,where it lies during the threading operation, to the large diameter portion after the threading of the yarn is finished.
The yarn hooking means may take the form of a grooved portion at the edge of the large diameter portion, or a projected portion formed at this edge. When the thread line from upstream to the small diameter portion is shifted towards the large diameter portion and the travelling yarn touches the peripheral surface edge on the side of the large diameter portion, the travelling yarn is caught by the hooking means during the rotation of the stepped roller and the travelling yarn so caught mounts onto the surface of the large diameter portion during one rotation of the stepped roller.
It is preferable that the part of the yarn hooking means which catches the yarn be at right angles to, or form an acute angle with, a plane perpendicular to the axis of the roller. The edge portion of the surface of the large diameter portion adjacent the small diameter portion may form an overhang to the end portion of the surface of the small diameter portion to facilitate the formation of a grooved portion on the edge portion and the catching of the travelling yarn. Two or more yarn hooking portions may be provided on the large diameter portion, where this diameter is particularly great.
The diameter of the large diameter portion of the stepped roller is selected according to the rotational speed of the roller and the desired peripheral speed. However in general the diameter may be selected in the range of from about 150 to about 300 mm, depending on the contact angle and contact length of the yarn to the peripheral surface, for giving a suitable transferring force to the yarn on the surface.
The stepped roller may be usually made of the material used for the conventional godet roller such as steel, for example S45C in Japanese Industrial Standard. It is preferable that the surface of the small diameter portion is finished with a finely dotted or "pebbly" surface finish, or with a fine slitted surface in which the direction of the slits intersects with the direction of the thread line on the surface, preferably with the direction of the slits substantially along the direction of the axis of the roller, for making the surface of the small diameter portion slippery to the travelling yarn on the surface, so as to facilitate the drawing off of the yarn from the small diameter portion by the suction nozzle.
The ratio of the peripheral speed of the large diameter portion and the peripheral speed of the small diameter portion is preferably selected in the range of from about 1.5 : 1 to about 5 : 1 according to conditions of yarn speed, ability of suction nozzle, etc.
The concept of the invention is applicable to the feeding of the travelling yarn having a low speed, however, the merit of the invention is obtained more clearly on yarn feeding apparatus which transfers the yarn with a speed of not less than 3,500 m/min.
The yarn feeding apparatus according to the invention is preferably used in combination with a well-known spinning apparatus for a synthetic polymer such as polyamide and polyester because the speed of the yarn drawn away from the spinning apparatus is capable of being changed automatically in a comparatively wide range following a high transferring speed during normal feeding of the yarn or following a comparatively low transferring speed during threading of the yarn whilst sucking the yarn with the section nozzle.
The yarn feeding apparatus according to the invention can be used to draw a freshly spun yarn in order to perform an orientation of the molecules in the yarn. In such a case, usually two rollers having different speeds are used in a feeding apparatus. The first roller positioned upstream has a lower peripheral speed. Where the peripheral speed of the first roller is comparatively low, it is possible to use a normal roller, that is a non-stepped roller, as the first roller. The stepped roller is used as the second roller having a higher peripheral speed than the first roller together with the yarn shifting means associated with the stepped roller. On the other hand, where the peripheral speed of the first roller is comparatively high, a stepped roller is used as the first roller together with the yarn shifting means and another stepped roller is used as the second roller having higher peripheral speed than the first roller, and in this case, it is not necessary to have a yarn shifting means positioned before 'the second stepped roller.
Means for shifting the travelling yarn position itself is well-known in the textile field. For example, one system is that a yarn guide holds the travelling yarn at one position and the yarn guide itself moves to another position in order to shift the travelling yarn; another system is that a first stationary yarn guide holds the travelling yarn at one position and just releases the travelling yarn held in it, whereupon a second stationary yarn guide positioned at the required position catches the travelling yarn released from the first stationary yarn guide which has simply moved to the second yarn guide under the influence of the tension of the travelling yarn.
In the accompanying drawings :

Figure 1 illustrates a schematic perspective view of one embodiment of the yarn feeding apparatus in accordance with the present invention;
Figure 2 illustrates a schematic perspective view of another embodiment of the yarn feeding apparatus in accordance with the present invention;
Figure 3(a), (b), (c) and (d) illustrate partial side views of four different stepped rollers which can be employed in the yarn feeding apparatus in accordance with the present invention;
Figure 4 illustrates a schematic perspective view showing one example of a freshly spun_'yarn winding system in which the yarn feeding apparatus in accordance with the present invention is employed as a yarn feeding apparatus arranged between a spinning apparatus and a winding apparatus; and
Figure 5(a) and (b) illustrate a schematic front view and a schematic partial side view of another embodiment of the yarn feeding apparatus in accordance with the present invention respectively.

A first embodiment of the present invention is illustrated by the schematic perspective view of Figure 1. A yarn shifting guide 6 is provided at the upstream side of a stepped roller 1 and is allowed to move along the direction of the axis of the stepped roller 1. A stationary yarn guide 2 is disposed upstream of the yarn shifting guide 6. The yarn Y delivered from a yarn feeding source (not shown in Figure 1) is threaded on a small diameter portion lb of the stepped roller 1 via the stationary yarn guide 2 and the yarn shifting guide 6 and to a yarn taking-up apparatus (not shown in Figure 1) by a person by using a conventional suction nozzle. The yarn path during the threading operation is represented by the symbol Y₀. The stepped roller 1 comprises a large diameter portion la and a small diameter portion lb and yarn hooking means lc which is disposed on the edge of the peripheral surface of the large diameter portion on the stepped side. This yarn hooking means lc shown in Figure 1 is composed of a grooved portion formed by cutting off a part of the cylindrical circumferential surface of the large diameter portion la, but alternatively, instead of the groove, it may be a pin protruding from the edge of the peripheral surface and over the small diameter portion lb. In short, the yarn hooking means lc must have such a function that when the yarn shifting guide 6 moves to the left in Figure 1, the hooking means 1c picks up the yarn and delivers the yarn onto the large diameter portion of the stepped roller 1 as the stepped roller 1 rotates.
Next, the operation of shifting the yarn from the yarn path Y passing over the small diameter portion lb of the stepped roller 1 shown in Figure 1 to the yarn path Y₂ passing over the large diameter portion la will be explained. The yarn that is travelling the yarn path Y₀ represented by the solid line in Figure 1 is moved from the position represented by the numeral 6 to the position represented by the numeral 6' by shifting the yarn shifting guide 6. In this case, the yarn Y first takes the yarn path Y₁ extending from the position of the yarn shifting guide 6' to the small diameter portion lb. This yarn path Y₁ has an angle θ₁ relative to the yarn path Y₂ which is at right angles relative to the axis of rotation of the stepped roller 1. Since the yarn entering the roller generally has a tendency to move towards a direction where the angle θ₁ becomes zero (0) on account of the tension in the yarn, the yarn Y in this case too, moves leftwardly on the smaller diameter portion 1b and approaches the large diameter portion la. Next, as the yarn path Y₁ moves leftward and the yarn comes into contact with the edge portion of the large diameter portion la on the stepped side, it is caught in the groove of the yarn hooking means lc formed at this edge portion. The travelling yarn located upstream of the yarn hooking means lc comes to be rolled over the surface of the large diameter portion la as the stepped roller 1 is rotated, and the yarn Y located downstream of the yarn hooking means lc gradually comes off the surface of the small diameter portion lb. As the roller 1 rotates once, the yarn path comes right onto the surface of the large diameter portion la of the stepped roller 1, and then moves further to the left on the surface of the large diameter portion until θ₁ becomes zero where the path coincides with the yarn path Y₂, which is the normal yarn feeding thread line.
In a second embodiment of the present invention shown in Figure 2, the yarn feeding apparatus comprises the yarn shifting guide 6 and the stepped roller 1 both of which are shown in Figure 1, and further comprises another stepped roller 11. In Figure 2, the stationary guide 2 and the yarn shifting guide 6 seen in Figure 1 are not shown. The stepped roller 1 acts as a first roller and the stepped roller 11 acts as a second roller. The stepped roller 11 has the same construction as that of the stepped roller 1. The numerals 11a, 11b and 11c indicate a large diameter portion, a small diameter portion and a yarn hooking means respectively. The peripheral speed of the large diameter portion la of the first stepped roller 1 is lower than the peripheral speed of the large diameter portion lla of the second stepped roller 11. A drawing operation of the travelling yarn Y₂ is accomplished between the first stepped roller 1 and the second stepped roller 11. Yarn shifting from the small diameter portion 11b to the large diameter portion 11a of the stepped roller 11, which occurs after the yarn shifting from the small diameter portion 1b to the large diameter portion la of the first stepped roller 1 will now be explained by referring to Figure 2.
Even when the yarn shifting to the yarn path represented by the dotted line Y₂ in the upstream of the first stepped roller 1 is completed, the yarn still takes the yarn path Y₃ represented by the dot and dash line between the first stepped roller 1 and the second stepped roller 11. The yarn is fed to the large diameter portion la of the first stepped roller 1 along the yarn path Y₂ and the yarn is fed to the small diameter portion llb of the second stepped roller along the yarn path Y₃ having an angle 9₂ relative to the yarn path Y₂. Accordingly, the same phenomenon that occurs on the first stepped roller 1 during the yarn shifting also takes place on the second stepped roller and the yarn caught by the yarn hooking means llc of the second stepped roller 11 comes over the large diameter portion lla from the small diameter portion 11b during the rotation of the second stepped roller 11, and at last it moves to the yarn path Y₂ represented by the dotted line, thereby completing the yarn shifting to the normal yarn feeding thread line. It can be understood from the above explanation that a yarn shifting guide just upstream of the second stepped roller 11 is not necessary.
Figure 3 shows a few partial side views of stepped rollers preferably employed in the present invention. Figures 3(a) and (b) show stepped rollers having a grooved portion lc at the stepped edge of a large diameter portion la, and Figures 3(c) and 3(d) show a stepped roller having a projected portion 1c at the stepped edge of the large diameter portion 1a. It is preferable that the angle shown in Figure 3 is selected in the range of from 30° to 100°. The yarn hooking effect becomes great when the angle 0 is an acute angle, and the depth of the groove or the height of the projection can be reduced.
A third embodiment of the present invention will be explained with Figure 4. Figure 4 is a schematic perspective view showing an example of a freshly spun yarn winding system in which the yarn feeding apparatus in accordance with the present invention is applied as a yarn feeding apparatus arranged between a spinning apparatus and a winding apparatus. In this system, a molten polymer is extruded from a spinneret 15 provided in a spinning apparatus 14 to form filaments which compose a yarn Y. The filaments extruded from the spinneret 15 are cooled during passage through a cooling chimney 16 and are gathered in four separated strands on a stationary yarn guide 17. Each of the strands comprises one quarter of the number of the filaments extruded from the spinneret 15. A yarn Y composed of the four strands separated from each other travels downwards and is oiled by contact with an oiling roller 18, and further travels downwards. Downstream of the oiling roller 1S, a stationary yarn guide 2, a yarn feeding apparatus 3, a stationary yarn guide 4, four stationary yarn guides 4' and a winding apparatus 9 are provided along a thread line to the winding apparatus 9 in this order. The yarn feeding apparatus 3 is constructed as a yarn feeding apparatus shown in Figure 2, that is, a yarn shifting guide 6 (shown in Figure 1 but not in Figure 2), a first stepped roller 1 which has a large diameter portion la, a small diameter portion 1b and a yarn hooking means lc, and a second stepped roller 11 which has a large diameter portion lla, a small diameter portion 11b and a yarn hooking means llc. The winding apparatus 9 is a well-known four bobbin spindle drive winder, which includes a spindle 7 positively driven by a driving means, four bobbins 5 mounted on the spindle 7 separately from each other, four yarn traverse means (behind the bobbins 5), each disposed adjacent to one of the bobbins 5 and all installed in a traverse mechanism 8, four retractable yarn guides 10 provided outside the yarn traverse range of each traverse means, and four setting yarn guides (behind the bobbins 5), one provided between each of the retractable yarn guides 10 and each of the bobbins 5. Symbol A in Figure 4 represents a yarn hooking detector which detects the completion of the yarn threading operation to each of the setting yarn guides in the winding apparatus 9. When the signal from A is delivered to a controller C, the signal controls the position of the yarn shifting guide 6. Symbol B represents a yarn path detector. When the signal of this detector B is delivered to a controller D, the signal controls the position of the retractable yarn guides 10.
Next, the method of operating this apparatus will be explained. When the first stepped roller 1 and the second stepped roller 11 in the yarn feeding apparatus 3, and the winding apparatus 9 are operated, the surface speed of the large diameter portions of the stepped rollers 1 and 11, and the surface speed of the bobbins 5 are set to 6,000 m/min., respectively. In this embodiment, drawing or stretching of the yarn does not occur between the first stepped roller 1 and the second stepped roller 11 because of both of the rollers having the same peripheral speed. The ratio of the diameter between the large diameter portion and the small diameter portion of each stepped roller is set to 2 : 1 in this embodiment. The yarn shifting guide 6 is positioned so as to be opposite the small diameter portion lb of the first stepped roller 1 and the retractable yarn guides 10 are in their projected positions. Spinning of the filaments is started.
When the operation of each part reaches a normal and steady state, the yarn travelling downwards from the spinneret 15 is sucked and drawn off by a conventional suction nozzle (not shown in Figure 4), handled by a person in usual manner, just upstream of the stationary yarn guide 2. The yarn is threaded on the stationary yarn guide 2 and also threaded on the oiling roller 18 under the control of the person with the suction nozzle. After threading the yarn Y on the stationary yarn guide 2, the yarn is threaded on the yarn shifting guide 6 which is located opposite the small diameter portion lb of the rotating first stepped roller 1 on the small diameter portion 11b of the rotating second stepped roller 11 and on the stationary yarn guide 4 by the operator whilst the travelling yarn is sucked into the suction nozzle. And further the travelling yarn is threaded on the stationary yarn guides 4' in a state separated into the four strands and each of the strands passing the stationary yarn guide 4' is guided to one of the setting yarn guides through one of the retractable yarn guides 10: these keep the travelling yarn running to the suction nozzle through the respective setting yarn guides arranged beyond the traverse range of each of the traverse means installed in the traverse mechanism 8. Then, the setting yarn guides act to make the strands touch the bobbins 5, and each of the bobbins 5 catches its respective strand by means of a well-known yarn catching means such as a ratchet disposed at the end portion of the bobbin or a blade cut disposed on the bobbin. When the yarn threading to the bobbins 5 is completed, the yarn Y is wound on to the surface of the bobbins 5. Since the retractable yarn guide 10 is projected in this instance, the yarn does not enter the traverse zone of the winding apparatus 9 and is wound in a bunch at an end portion of the bobbins.
Then, the yarn hooking detector A detects the completion of the yarn hooking and its signal is delivered to the controller C whereby the controller C transmits a signal to the air cylinder 13. The air cylinder 13 is operated by the signal and moves the yarn shifting guide 6 from the position opposite the small diameter portion to the position opposite the large diameter portion. By moving the yarn shifting guide 6, the yarn path is changed from the yarn path Y_O passing the small diameter portion to the path Y₂ leading to the large diameter portion as explained above with reference to Figures 1 and 2.
The yarn path detector B detects completion of the movement of the yarn path and its signal is delivered to the controller D whereby the controller moves the retractable yarn guides 10 backward by suitable means (such as a solenoid, for example) whereupon the yarn enters into the operation zone of the traverse mechanism 8 from the position of the bunch-winding and the normal winding operation is thus initiated.
In the yarn feeding apparatus in accordance with the present invention, the yarn threading operation is performed at a low travelling speed of the yarn and the normal operation of winding at a high speed is initiated when the yarn threading operation is completed. Even when the yarn is taken up at a speed of 6,000 m/min., the yarn threading operation is performed at a yarn speed of about 3,000 m/min. Hence, the suction nozzle to be used in the threading of the yarn may be of a conventional, ordinary type. In addition, the movement of the yarn path can be accomplished within a short period of time such as from about 0.2 to about 0.5 seconds, for example. When a yarn of 75-deniers is to be wound, for example, the yarn quantity to be wound in a bunch from the completion of the yarn threading until the start of the normal winding is only about 0.2 to about 0.4g. The treatment of waste yarn of such an extent can be made after the bobbin becomes full. With a yarn of this size, the movement of the yarn path from Y₀ to the point where yarn is just rolled up on the large diameter portion is automatically performed within about 0.1 seconds. Hence there is no practical problem at all in this respect.
In Figure 5, a fourth embodiment of the present invention will be explained. In the yarn feeding apparatus in accordance with the present invention, no trouble occurs if the distance between the stepped roller 11 and the stationary yarn guide 4 shown in Figure 4 is large. If this distance is small, however, since the stationary yarn guide 4 is generally positioned so as to match with the yarn path Y₂, that is, the yarn path passing the large diameter portion, the yarn is sometimes caught by the yarn hooking means llc of the stepped roller 11 and comes over the large diameter portion even when the yarn path should be Y₀, that is, over the small diameter portion. Accordingly, it is advisable to arrange a yarn path regulating guide 12 such as shown in Figure 5.
Figure 5 is a schematic view useful for explaining the shape and position of the abovementioned yarn path regulating guide 12, Figure 5(a) being a front view and Figure 5(b) being a partial side view of Figure 5(a). In Figure 5 the yarn path regulating guide 12 is disposed at an intermediate position between the stepped roller 1 and the stationary yarn guide 4 so that when the yarn is in the yarn path Y_OP the guide 12 comes into contact with the yarn and regulates the yarn path, whilst it does not come into contact with yarn in the yarn path Y₂. Furthermore, as shown in Figure 5(b), the guide 12 is positioned so as to be opposite the small diameter portion 1b of the stepped roller 1 on the side close to the large diameter portion la. Accordingly, when the yarn is in the yarn path Y₀, the yarn is restricted by the yarn path regulating guide 12 and does not move towards the large diameter portion la, but when the yarn path moves from Y₀ to Y₂ to the right in Figure 5(b), the yarn comes off the yarn path regulating guide 12 and perfectly moves to the yarn path Y₂. Accordingly, the yarn path does not change suddenly from Y₀ to Y₂ during the yarn threading operation to the winding apparatus and the movement of the yarn is made only after the movement of the yarn shifting guide 6. Hence, the operation can be carried out in a reliable way.
Further, the embodiment of the present invention shown in Figure 5 includes a normal roller 31, that is a non-stepped roller, which is a first roller of the yarn feeding apparatus. The stepped roller 1 acts as a second roller of the yarn feeding apparatus. The small diameter portion 1b of the stepped roller 1 has a pebbly surface to make the surface slippery for the travelling yarn. The pebbly surface consists of minute rounded hills and valleys on all portions of the small diameter portion coming in contact with the yarn, and this effect can be obtained by sandblasting, blasting the surface with liquid particles, or etching. The peripheral speed of the large diameter portion la of the stepped roller 1 is higher than the peripheral speed of the first roller 31 so as to occasion a drawing or stretching of the yarn. Where the peripheral speed of a roller used in the yarn feeding apparatus is low, that is not more than about 4,000 m/min., there is no need of the stepped roller. The embodiment shown in Figure 5 is useful in the case when the peripheral speed of the first roller 31 is not more than about 4,000 m/min. and the peripheral speed of the second roller is not less than about 4,000 m/min. Further, it can be seen that the second roller 1 incorporates a pair of yarn hooking means Ic located diametrically opposite each other on the peripheral edge of the stepped surface of roller 1. In general, any number of yarn hooking means may be employed.
Since with the yarn feeding apparatus in accordance with the present invention the yarn threading operation is performed at the low speed of the travelling yarn which traverses the small diameter portion in the yarn feeding apparatus to the bobbin of the yarn winding apparatus, the yarn threading operation is simple. Further, the ordinary conventional suction nozzle can be employed for this yarn threading operation and the consumption of pressured air is small. In comparison with other high speed yarn feeding apparatus, the installation expense as well as the cost of operation can be reduced. Further, the pressurised air generation installation may be compact in size and the floor space requirement becomes smaller. Noise is also less and the work environment can be improved. Next, the time required for the yarn threading operation is shorter and there is less occurrence of waste yarn.

Claims

1. A yarn feeding apparatus for transferring a synthetic yarn supplied continuously from a yarn supply source to a yarn taking-up apparatus characterised in that it comprises

(a) a stepped roller, positively rotated by driving means, which has a large diameter portion over which the travelling yarn passes during the normal feeding of the yarn, a small diameter portion over which the travelling yarn passes during the threading operation of the yarn from the varn supply source to the yarn taking-up apparatus through the yam feeding apparatus, and yarn hooking means at the edge of the peripheral surface of the large diameter portion on the side adjacent the small diameter portion, and

(b) means arranged at the upstream side of the stepped roller for shifting the path of travelling yarn from the small diameter portion to the large diameter portion.

2. A yarn feeding apparatus as claimed in claim 1 wherein said yarn hooking means is a grooved portion formed at the edge of the peripheral surface of the large diameter portion.

3. A yarn feeding apparatus as claimed in claim 1 wherein said yarn hooking means is a projected portion formed at the edge of the peripheral surface of the large diameter portion.

4. A yarn feeding apparatus as claimed in any one of the preceding claims wherein at least a part of the peripheral surface of said small diameter portion is formed with a pebbly surface to make the surface slippery for the travelling yarn.

5. A yarn feeding apparatus as claimed in any one of claims 1 to 3, wherein at least a part of the peripheral surface of said small diameter portion is formed with a fine slitted surface to make the surface slippery for the travelling yarn.

6. A yarn feeding apparatus as claimed in any one of the preceding claims wherein the diameter of said large diameter portion and the diameter of said small diameter portion are selected so that the peripheral speed of the large diameter portion is in the range of from about 1.5 to about 5 times higher than the peripheral speed of the small diameter portion.

7. A yarn feeding apparatus as claimed in any one of the preceding claims wherein the peripheral speed of the large diameter portion is not less than 3,500 m/min.

8. A yarn feeding apparatus as claimed in any one of the preceding claims wherein the peripheral speed of the small diameter portion is not more than 4,000 m/min.

9. A yarn feeding apparatus as claimed in any one of the preceding claims having downstream of said stepped roller a second stepped roller positively rotated by driving means, which has a large diameter portion over which the travelling yarn passes during the normal feeding of the yarn, a small diameter portion over which the travelling yarn passes during the threading operation of the yarn from the yarn supply source to the yarn taking-up apparatus through the yarn feeding apparatus and yarn hooking means at the peripheral surface of the large diameter portion on the side adjacent the small diameter portion, the peripheral speed of the large diameter portion of the first mentioned stepped roller being lower than the peripheral speed of the large diameter portion of the second stepped roller so that the yarn is drawn between the stepped rollers during the normal feeding of the yarn.

10. A yarn feeding apparatus as claimed in any one of claims 1 to 8 wherein a non-stepped roller having a peripheral speed of not more than 4,000 m/min. and positively rotated by driving means is arranged upstream of said stepped roller, the peripheral speed of the non-stepped roller being lower than the peripheral speed of the large diameter portion of the stepped roller so that the yarn is drawn between the non-stepped roller and the stepped roller during the normal feeding of the yarn.

11. A yarn feeding apparatus as claimed in any one of the preceding claims wherein said yarn supply source is a spinning apparatus to extrude a molten polymer for forming filaments which compose the yarn.

12. A yarn feeding apparatus as claimed in any one of the preceding claims wherein said yarn taking-up apparatus is a yarn winder/which a bobbin is mounted.